SQL Server - 带CASE的WHERE子句

Question

ALTER PROCEDURE GetVendor_RMA_CreditMemo
    (@HasCreditMemoNo INT)
BEGIN
    SELECT 
        * 
    FROM
        (SELECT
             CreditMemoNumber,
             CASE WHEN CreditMemoNumber != '' 
                     THEN 1
                     ELSE 0 
             END AS HasCreditMemoNo   
         FROM
             XYZ) as C
    WHERE
        (C.HasCreditMemoNo = @HasCreditMemoNo OR @HasCreditMemoNo = -1)
END 

CreditMemoNumber是varchar专栏

我想实现这个目标：

CASE 
   WHEN @HasCreditMemoNo = 0 
      THEN -- select all rows with no value in CreditMemoNumber Column,  
   WHEN @HasCreditMemoNo = 1 
      THEN -- all rows that has some data,   
   WHEN @HasCreditMemoNo = -1 
      THEN -- everything regardless..

Answer 1

你不能用CASE来做这件事。

正确的方法是使用OR：

WHERE (@HasCreditMemoNo = 0 AND {no value in CreditMemoNumber Column})
OR   
     (@HasCreditMemoNo = 1 AND {all rows that has some data})
OR
     (@HasCreditMemoNo = -1)

Answer 2

这对你有用吗？我不确定它是否会改善你的表现。你可能最好写一个if else if else语句和三个单独的select语句，在CreditMemoNumber列上有一个索引。

ALTER PROCEDURE GetVendor_RMA_CreditMemo(@HasCreditMemoNo int)
BEGIN
    select
       CreditMemoNumber,
       case when CreditMemoNumber != '' then 1 else 0 end as HasCreditMemoNo 
    from XYZ
    where
        (@HasCreditMemoNo = 0 and (CreditMemoNumber is null or CreditMemoNumber = ''))
        or (@HasCreditMemoNo = 1 and CreditMemoNumber != '')
        or (@HasCreditMemoNo = -1)
END